在字符串中添加空格

char * addSpaces(char * s, int* spaces, int spacesSize){
    int n = strlen(s);
    char *a = (char*)malloc(sizeof(char) * (n + spacesSize + 1));
    int j = 0;
    int idx = 0;   
    for (int i = 0; i < n; i++) {
        if (j < spacesSize && i == spaces[j]) {
            j++;
            a[idx++] = ' ';
        }
        a[idx++] = s[i];
    }
    a[idx] = '\0';
    return a;
}